Digital based electronic media formats are finally on the cusp of largely replacing analog electronic media formats. Digital compact discs (CDs) replaced analog vinyl records long ago. Analog magnetic cassette tapes are becoming increasingly rare. Second and third generation digital audio systems such as Mini-discs and MP3 (MPEG Audio−layer 3) are now taking market share from the first generation digital audio format of compact discs.
The video media has been slower to move to digital storage and transmission formats than audio. This has been largely due to the massive amounts of digital information required to accurately represent video in digital form. The massive amounts of information require very high-capacity digital storage systems and high-bandwidth transmission systems.
However, video is now rapidly moving to digital storage and transmission formats. The DVD (Digital Versatile Disc), a digital video system, has been one of the fastest selling consumer electronic products in years. DVDs have been rapidly supplanting Video-Cassette Recorders (VCRs) as the pre-recorded video playback system of choice due their high video quality, very high audio quality, convenience, and extra features. The antiquated analog NTSC (National Television Standards Committee) video transmission system is now being replaced with the digital ATSC (Advanced Television Standards Committee) video transmission system.
Computer systems have been using various different digital video formats for a number of years. Among the best digital video compression and encoding systems used by computer systems have been the digital video systems backed by the Motion Pictures Expert Group known as MPEG. The three most well known and highly used digital video formats from MPEG are known simply as MPEG-1, MPEG-2, and MPEG-4. (The MPEG-2 digital video compression and encoding system is used by DVDs.)
The MPEG-2 and MPEG-4 standards compress a series of video and encode the compressed frames into a digital stream. Video frames may be compressed as Intra-frames or Inter-frames. An Intra-frame independently defines a complete video frame. An Inter-frame defines a video frame with reference to other video frames, previous or subsequent to the current frame.
When compressing video frames, an MPEG-2 and MPEG-4 encoder usually implements a ‘rate controller’ that is used to allocate a ‘bit budget’ for each video frame that will be compressed. The bit budget specifies the number of bits that have been allocated to encode the video frame. By efficiently allocating a bit budget to each video frame, the rate controller attempts generate the highest quality compressed video stream without overflowing buffers (sending more information than can be stored) or underflowing buffers (not sending frames fast enough such that the decoder runs out of frames to display). Thus, to best compress and encode a digital video stream, a digital video encoder needs a good rate controller. The present invention introduces new methods and systems for implementing a rate controller for a digital video encoder.